How can start a subprocess in user task working

I designed the process:
QQ截图20220721181431

I want start a subprocess in the working user task, but there is no follow-up after the boundary event is triggered, The CallActivity task does not work.

thanks for reply.

the bpmn:

<?xml version="1.0" encoding="UTF-8"?>
<bpmn2:definitions xmlns:bpmn2="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" xmlns:flowable="http://flowable.org/bpmn" targetNamespace="">
  <bpmn2:signal id="startSubprocessSignal" name="startSubprocessSignal" flowable:scope="processInstance" />
  <bpmn2:process id="call_activity" name="call_activity" isExecutable="true">
    <bpmn2:startEvent id="StartEvent_1" name="initial">
      <bpmn2:outgoing>Flow_1usv8kc</bpmn2:outgoing>
    </bpmn2:startEvent>
    <bpmn2:sequenceFlow id="Flow_1usv8kc" sourceRef="StartEvent_1" targetRef="Activity_1omcw0p" />
    <bpmn2:userTask id="Activity_1omcw0p" name="user task woking" flowable:candidateUsers="">
      <bpmn2:incoming>Flow_1usv8kc</bpmn2:incoming>
      <bpmn2:outgoing>Flow_077ur4l</bpmn2:outgoing>
    </bpmn2:userTask>
    <bpmn2:endEvent id="Event_1rn09v7" name="end">
      <bpmn2:incoming>Flow_077ur4l</bpmn2:incoming>
    </bpmn2:endEvent>
    <bpmn2:sequenceFlow id="Flow_077ur4l" sourceRef="Activity_1omcw0p" targetRef="Event_1rn09v7" />
    <bpmn2:callActivity id="Activity_1pmtq8k" name="subprocess" calledElement="${subprocessDefinitionKey}">
      <bpmn2:incoming>Flow_05aojyo</bpmn2:incoming>
      <bpmn2:outgoing>Flow_0jd1fs2</bpmn2:outgoing>
    </bpmn2:callActivity>
    <bpmn2:endEvent id="Event_08gtzvz" name="subprocess end">
      <bpmn2:incoming>Flow_0jd1fs2</bpmn2:incoming>
    </bpmn2:endEvent>
    <bpmn2:sequenceFlow id="Flow_0jd1fs2" sourceRef="Activity_1pmtq8k" targetRef="Event_08gtzvz" />
    <bpmn2:boundaryEvent id="Event_0js2px8" cancelActivity="false" attachedToRef="Activity_1omcw0p">
      <bpmn2:outgoing>Flow_05aojyo</bpmn2:outgoing>
      <bpmn2:signalEventDefinition id="SignalEventDefinition_06rtorz" signalRef="startSubprocessSignal" />
    </bpmn2:boundaryEvent>
    <bpmn2:sequenceFlow id="Flow_05aojyo" sourceRef="Event_0js2px8" targetRef="Activity_1pmtq8k" />
  </bpmn2:process>
  <bpmndi:BPMNDiagram id="BPMNDiagram_1">
    <bpmndi:BPMNPlane id="BPMNPlane_1" bpmnElement="call_activity">
      <bpmndi:BPMNEdge id="Flow_0jd1fs2_di" bpmnElement="Flow_0jd1fs2">
        <di:waypoint x="362" y="350" />
        <di:waypoint x="412" y="350" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="Flow_077ur4l_di" bpmnElement="Flow_077ur4l">
        <di:waypoint x="362" y="178" />
        <di:waypoint x="412" y="178" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="Flow_1usv8kc_di" bpmnElement="Flow_1usv8kc">
        <di:waypoint x="208" y="178" />
        <di:waypoint x="262" y="178" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="Flow_05aojyo_di" bpmnElement="Flow_05aojyo">
        <di:waypoint x="310" y="236" />
        <di:waypoint x="310" y="310" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNShape id="_BPMNShape_StartEvent_2" bpmnElement="StartEvent_1">
        <dc:Bounds x="172" y="160" width="36" height="36" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="177" y="203" width="26" height="14" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Activity_0ewk2d0_di" bpmnElement="Activity_1omcw0p">
        <dc:Bounds x="262" y="138" width="100" height="80" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Event_1rn09v7_di" bpmnElement="Event_1rn09v7">
        <dc:Bounds x="412" y="160" width="36" height="36" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="421" y="203" width="19" height="14" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Activity_039if8r_di" bpmnElement="Activity_1pmtq8k">
        <dc:Bounds x="262" y="310" width="100" height="80" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Event_08gtzvz_di" bpmnElement="Event_08gtzvz">
        <dc:Bounds x="412" y="332" width="36" height="36" />
        <bpmndi:BPMNLabel>
          <dc:Bounds x="391" y="375" width="78" height="14" />
        </bpmndi:BPMNLabel>
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Event_1k0ecwh_di" bpmnElement="Event_0js2px8">
        <dc:Bounds x="292" y="200" width="36" height="36" />
      </bpmndi:BPMNShape>
    </bpmndi:BPMNPlane>
  </bpmndi:BPMNDiagram>
</bpmn2:definitions>

I’m not sure I fully understand what you’re asking here. How are you firing the signal? Programmatically? What part isn’t working?

I sent the signal through the above API. No new processes are created afterwards.

I’m not sure i understand what you are asking.
Are you saying the signal isn’t “triggering”?
Or are you saying, after the signal “triggers”, the called activity is not called?
You say you are triggering the SIgnal boundary event via the REST API.
What, exactly, is the URL you are calling?